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<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var arr = [1500, 1200, 2000, 2100, 1800]
        var newArr = []
        for (var i = 0; i <= arr.length-1; i++) {
            if (arr[i] < 2000) {
                // newArr[newArr.length] = arr[i];
                newArr.push(arr[i])
            }
        }
        console.log(newArr)
    </script>
</body>
</html>